GSSP for Tremadocian Stage

Definition:

The base of the Ordovician System and base of the lowest Ordovician
stage (Tremadocian) is exposed in the coastal platform at Green Point,
western Newfoundland, at 101.8m level, within Bed 23, in the measured
section (Lower Broom Point Member, Green Point Formation), coinciding
with the first appearance of the conodont Iapetognathus
fluctivagus, and 4.8m below the earliest planktonic
graptolites.

Location:

The Green Point Section is located within the Gros Morne National Park, about
70km from Deer Lake Airport and about 10km north of the village of Rocky
Harbour, western Newfoundland.

Sedimentology:

The Green Point Section is comprised of alternating black, grey and
green shales, micritic nodular and ribbon limestone and grainstone.
Limestone conglomerate is largely confined to one bed (Bed 19) and a
lenticular bed within Bed 25.

Primary Markers:

First appearance of conodont species Iapetognathus fluctivagus
within Bed 23.

Secondary Markers:

Graptolites:
Planktonic graptolites appear 4.8m above the boundary in the Green
Point Section. The earliest planktonic graptolite species ,
Staurograptus dichotomus and Rhabdinopora praeparabola,
are both present in the Green Point Section.Carbon isotopes:
The boundary level coincides closely with the peak of a positive cycle
in Î´13C,
representing the highest value reached in the boundary interval.

Correlation Events:

Conodont FAD Iapetognathus fluctivagus

Other Locations around the World:

The Cambrian-Ordovician Boundary lies in the lower Ibex Series of
North America, at the base of the Warendian Stage of north Australia,
in the lower Tremadoc as used in Kazakhstan, and in the late
Fengshanian of north China.